32S-1/3 Service Information

The following items are intended to be used as aids in troubleshooting

On 27 July 1971, Amateur Product Line Information Letter No. 28 was issued which contained the following information:
OVERCOME INSTABILITY CAUSED BY AGING
Some 32S-1 and early KWM-2 Transceivers are beginning to exhibit various forms of instability that fails to respond to usual corrective efforts.
A common cause is capacitor C56 in the 32S-1 and C123 in the KWM-2. These are axial-lead ceramic feedthrough capacitors which are mounted immediately to the right of the 6CL6 driver tube in the PA cage. As they age, they become frequency sensitive.
At one time the typical symptom of a defective capacitor was for the transmitter to operate properly on all bands except 15 metres, where it would oscillate. More recent reports include almost any set of instability symptoms you might describe.
The conclusion is, that if an older unit shows instabilities, the above mentioned capacitors should be changed before other repair efforts are made. For a number of years a mica feedthrough capacitor (CPN 912-5232-000) has been used in the 32S-1 and KWM-2 with complete success. The hole vacated by the old capacitor will have to be enlarged slightly to accomodate the new capacitor.
Another problem that is difficult to determine involves instability and eventually oscillation appearing first on the 80 metre band, and then including 40, etc. This is caused by the fact that over a period of time aluminium will become covered with oxide. In spite of finger stock between the shield cans over the RF coils and band switch wafers, the cans eventually become floating which allows feedback to occur.
32S-1 service bulletins:
SB-1 Improve VOX operation.
SB-2 Improve carrier suppression.
SB-3 Add VOX relay time constant.
SB-4A To improve CW operation.
I noticed a posting not to long ago about problems with sidetone quality/stability in the 32S-3.
First, V11 is set up as an R-C phase shift osc. The frequency determined by the phase shift feedback network from pin 6 (plate) to pin 2 (grid). As the case with most R-C oscillators, small voltage fluctuations will change the frequency ever so slightly.
The tone oscillator is activated by providing a ground to the cathode-bias resistor, R66, through the mode switch during tune, lock-key, and cw. During LSB and USB, the cathode is left "floating".
If you look closely, C6B, 25uF @ 25V filters the cathode to ground. When the ground is lifted from R66 during LSB and USB, C6B is still connected from cathode to ground and allowed to charge (slowly) close to the plate potential of V11, about 150V. Not good for a cap rated at 25V !!! C6B has a very short life.
(This is quite noticeable when the rig is allowed to sit in USB or LSB for a length of time, then switching immediately to CW or TUNE. The Tone will sag as C6B levels out and discharges.)
C6B is also the "B" side of C6A. (the 8uF filter for the +275V plate line.)
The fix is easy.
1. Clip the excessively long wire out (completely) from C6B (and C6B only !) to pin 7 of V11.
2. Install a 50uf, 50V cap ACROSS R66. By placing this across R66, the cap is only switched in circuit when needed and COMPLETELY shuts off the tone osc. when not in use. (no more modulated B+lines or "phantom" tone !!)
Adding a 5uF 400V lytic from the junction of R63/R62 to ground will stop the "voltage jerk" during break in keying.
3. Last but least, replace C107 with a high-stability metal-film or poly cap of equal value.
Steve Uckerman, N2JXL

Getting a good carrier null from the balanced mixer can be achieved in one of the following null procedures.

Service Bulletins

32S-1 Transmitter
PUB NO.	NOTE	DATE	 DESCRIPTION
SB 1		6/30/59	 Improve VOX Operation
SB 2	 	4/1/60	 Improve Carrier Suppression
SB 3	 	8/8/60
                Revised
                10/1/60
                10/13/67 Add VOX Relay Time Constant Control
SB 4		8/21/61	 (Superseded by 32S-1 SB 4A)
SB 4A	 	2/20/62	 To Improve CW Operation
SIL 0-59	7/28/59	 Use as CW or AM Exciter
SIL 1-75	10/15/75	Overcome Instability Caused By Aging
SIL 2-75	10/15/75	Extended Operating Range
SIL 0-60	2/3/60	 VFO Oscillator Drift

32S-2 Transmitter
PUB NO.	NOTE	DATE	 DESCRIPTION
SB 1			 Not Issued
SB 2	 	4/1/60	 Improve Carrier Suppression
SB 3	 	8/8/60
                Revised
                10/1/60
                10/13/67 Add VOX Relay Time Constant Control
SB 3		8/8/60
Revised
10/1/60
10/13/67	Add VOX  Relay Time Constant Control
SB 4			 Not Issued
SB 4A	 	2/20/62	 To Improve CW Operation
SIL 2-75	 	 10/15/75	Extended Operating Range

32S-3 Transmitter
PUB NO.	NOTE	DATE	 DESCRIPTION
SB 1		8/8/67
                Revised
                8/31/67
                10/13/67 Improve VOX Circuit to Eliminate Intermittent Dropout
                         and Improve Operation of First Audio Amplifier 
                         (Supersedes 32S-1 SB 4, and 32S-3 SB 5 and 6)
SB 2		9/21/67	 Removal of Audio Distortion
SB 3, 4			 Not Issued
SB 5		6/11/63	 (Superseded by 32S-3 SB 1)
SB 6		7/10/64
                Revised
                8/28/64	 (Superseded by 32S-3 SB 1)
SB 7		6/1/72
                Revised
                8/7/72
                10/15/75 Converts 32S-3 to 32S-3A
SIL 2-75	10/15/75 Extended Operating Range

32S-3A Transmitter
PUB NO.	NOTE	DATE	DESCRIPTION
SIL 2-75	10/15/75 Extended Operating Range

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